This document describes a device for taking samples, particularly pasty and muddy samples that can have very variable viscosity characteristics.
Some devices can be used to take fluid samples from a reservoir before they are forced out by the displacement of a piston that contributes to delimiting a chamber with variable volume into which the samples are drawn. One of these devices, known to everyone, is a syringe. Another device developed by the applicant for taking mud samples, is described in French patent booklet 2 700 851. It comprises a membrane formed by a circular elastic casing, that is inflated to close off the sampling chamber and is deflated to open it. The area of the opening may be equal to the cross-section of the chamber (cylindrical) if the casing continues along the line of the wall of the chamber when it is deflated, which means that very viscous samples can be drawn in easily without them being disturbed by flow irregularities. However, this device can only be used to take samples on site, whereas it is often more convenient and less dangerous, or advisable for other reasons, to take samples passing through a pipe.
With another type of fluid sample-taking device, an example of which is described in French patent 2 747 780, the product to be sampled is drawn in precisely through a pipe with two adjacent elbows interrupted in front of these elbows. The edge of the receptacle in which the sample is to be collected is placed around the elbows, such that the receptacle restores continuity of the pipe and the product drawn in passes through it. This device is particularly simple, and the regularity of the pipe cross-section is such that different viscosities of samples can be taken without very much changing their physical composition; But it is not possible to control the sampled volume, except by choosing a receptacle with the required volume, which is not very convenient and is sometimes impossible under real circumstances in laboratories; furthermore, receptacles are open, which means that they must be kept within a protection chamber if the samples are dangerous.
The essential purpose of the invention is to safely and simply take fluid samples that can have variable and possibly high values of viscosity and cloudiness. In particular, it is desirable not to have to dip the sampling device into the product, and to keep the sampled product within an entirely closed and sealed volume for the time necessary to transport it or to submit it to a first examination without being exposed to the product; the sample may be refused and rejected without having taken any risk.
The device comprises a body inside which there is a rotating plug through which two drillings have been made, separated by an angle equal to an angle separating two orifices penetrating the body and leading into an intake pipe and a discharge pipe for the unsampled part of the effluent, the body also being perforated by a sample-taking orifice provided with a calibrated valve located between the bottom of a cylindrical chamber contained in the body and partially delimited by the rotating plug, the device also comprising a piston free to move in the rotating plug towards and away from the bottom and delimiting the chamber on the side opposite the bottom.
Note that although some elements according to prior are present in the invention, they are combined in an innovative manner that can be considered to be unexpected; the use of a body and a rotating plug makes one think of a valve, but valves are only designed to enable and interrupt a flow without enabling collection of a sample of the flowing liquid in themselves; there is a piston that varies the volume of a chamber, but this piston does not draw the sample into the chamber; finally, the sample is formed by creating a flow that passes through a chamber for which the contents are to be sampled, but this chamber is not included in a removable flask as in earlier designs.
The seal of the device and its ease of maintenance are better if the bottom of the chamber is delimited by a base of the rotating plug, the sampling orifice is located on a circumference of the body common to the inlet and discharge orifices, and is separated from one of the inlet and outlet orifices by the angle between the drillings in the rotating plug.
In one particularly simple embodiment of the structure, an opening is formed in the body opposite the bottom of the chamber, the rotating plug projects from the body at the said opening, the piston is coupled to a manoeuvring device fitted with a portion engaged by a thread on the rotating plug; the sampled volume may be adjusted very easily if the said portion of the manoeuvring device is a skirt covering the rotating plug and if the graduations are marked on the rotating plug, to be covered by the skirt when the piston is displaced.